Determining whether your stove will be efficient?
For the stoves we sell, we always include information on efficiency. However, what do these numbers mean and where do they originate from?
All Bowland Stoves Ltd stove product pages contain efficiency data for that individual item, which is located under the Technical Tab. The heat output amount, which will be clearly shown in kilowatts, for example 5kW, and should not be confused with this.
The efficiency statistic, which will be displayed as a percentage, is intended to inform you of the proportion of fuel that will be used to heat your space vs the portion that will be wasted. Therefore, 25% of the heat that the fuel may possibly provide is lost up the chimney by an 75% efficient stove.
For comparison, the efficiency of an open fireplace is about 30%, which means that a staggering 70% of the energy is wasted.
The measuring process….
In accordance with criteria set by British and European standards bodies, stoves are commonly tested by independent energy consultancies.
However, the stove manufacturer is given considerable leeway as to the circumstances in which their appliance will be tested.
For example, they have the option to choose:
- the heat output at which the stove will be tested
- the size of the fuel burnt when the test is taking place
- how often the stove is refuelled, as long as it’s no less frequently than every 45 minutes
After that, the consultant takes measurements of the flue gases’ temperature and carbon content. These measures enable the tester to determine the amount of heat and fuel waste since attention is taken to know exactly how much fuel is being used. These numbers are used to calculate the stove’s efficiency.
The challenges of measuring stove efficiency…
Although knowing a stove’s prospective efficiency is helpful when making a purchase decision, there are several disadvantages to the measures.
A like-for-like comparison across brands becomes nearly difficult if each manufacturer is creating unique testing conditions for their stoves, as you have undoubtedly already thought about.
Another issue is that a manufacturer can easily modify the air supply, heat output, and refuelling time (by sealing vents) to reach the desired efficiency level.
In other words, you can’t always rely on stove efficiency numbers to tell you which stove will be the most efficient when you use it at the temperature you want, with the fuel you want to burn, and with the frequency you want to reload.
However….
The efficiency estimates are not without merit because everyone is allowed to create the best conditions for their burn, levelling the playing field.
Searching for Ecodesign stoves is a smart approach to find efficient stoves because new Ecodesign laws require higher efficiency for stoves marketed in the UK and EU. Two excellent examples are the Arada Ecoburn 5 (81.3% efficiency) and the Dunsley Avance 500 (81.2% efficiency).